The invention relates to an apparatus which is used for therapeutic treatment of a shoulder joint. In particular, the device can be used to impart continuous passive motion ("CPM") to a shoulder. This device is portable, and the device can be worn by the patient to allow for patient mobility. The device can impart both abduction and rotation to the shoulder.
Continuous passive motion therapy is used to aid in recovery following joint trauma and has been found to have beneficial results in the rehabilitation of injured limbs. Passive motion is also used for treatment of other bone and muscular disorders, such as arthritis and muscular dystrophy. Often a physical therapist must apply the passive motion.
Many devices are currently commercially available for application of continuous passive motion to the hip, leg and foot. An example of such a device is shown in German Offenlegungsschrift No. 25 24 468 to Lang. This publication also shows a device to cause flexion of the wrist and elbow. Other devices which cause continuous passive flexion of the elbow and wrist are illustrated in French Pat. No. 2,440,187 to Pecheux, U.S. Pat. No. 3,929,335 to Malick, and U.S. Pat. No. 4,487,199 to Sarringer.
It is more difficult to design a device to impart the desired passive treatment to the shoulder than to the elbow or wrist, in part because of its proximity to the torso, and in part because of the greater range of mobility in the shoulder. Devices for exercising the shoulder joint are shown in U.S. Pat. No. 2,777,439 to Tuttle, U.S. Pat. No. 3,089,700 to Hotas, and U.S. Pat. No. 4,395,039 to Kaiser.
The shoulder is formed where the clavicle, scapula and humerus join laterally. The joint formed is a ball-and-socket type articulation between the proximal humerus and the glenoid cavity of the scapula. The socket is shallow, and the joint capsule is loose-fitting. As a result of this construction, the joint permits a wide range of motion but the joint is subject to poor stability and strength.
The shoulder is capable of three types of motion: abduction and adduction, flexion and extension, and rotation. Abduction and adduction is movement of the arm away from and toward the median axis, or long axis, in the median plane of the body. The median plane of the body is defined by the front or back of the body in a straight position. Abduction is movement away from the median axis, such as raising an arm laterally or sideways. Adduction is the opposite movement, i.e., movement toward the median axis of the body. Flexion means moving the arm forward and upward or backward and upward to increase the angle between the arm and the median plane of the body. Extension is the opposite motion of flexion, i.e., movement toward the median plane of the body. Rotation is turning the arm about its long axis as if on a pivot. External rotation is rotation away from the median axis of the body and internal rotation is rotation toward the median axis of the body.
Following shoulder surgery, it is desirable to recover abduction and adduction, and rotation in the shoulder joint. If abduction and adduction can be recovered, flexion and extension will also be possible.
The current invention presents a device for passively inducing abduction and adduction of the arm about the shoulder, and optionally causing simultaneous rotation of the arm as well. The device fits against the lateral portion of the torso under the shoulder to be exercised and provides support for the upper arm and the forearm. It exercises the shoulder by raising the upper arm and forearm supports, which pushes the arm upward to cause abduction and external rotation, and by supporting the arm against its own weight to cause controlled adduction and internal rotation. The device permits variable angles of abduction and rotation, as well as variable speeds of motion.
Another feature of continuous passive motion devices which is desirable is portability. These devices may be transported from room to room in order to enable different patients to share a CPM machine.
It is of even further advantage if the device is designed to allow the patient to wear the device since the patient may be subjected to continuous treatment. The patient may thus remain mobile while being subjected to CPM treatment.
It is a further advantage to present a CPM unit which can be easily adapted for use with the right shoulder as well as the left shoulder.
It is also of advantage to provide a CPM structure which can be adjusted according to the angle of flexion desired at the elbow, and to adapt to patients of varying size and shape.
Finally, in the interests of safety, it is an advantage for the CPM device to be designed so that a minimum of the actuator mechanism is exposed. If the operating parts of the device are concealed, it reduces the risk of a patient's being pinched by the machine, or bed clothes getting caught in the mechanism.